The brochure of Heraeus Quarzschmelze GmbH entitled "INFRAROT, mittelwellige Bausatz-Infrarotstrahler MBS" [INFRARED, medium-wavelength modular set--Infrared lamp MBS] bearing printer's legend 1C 4.88/VN Ku, discloses lamp units in which the infra-red lamps are in the form of so-called "twin tubes" open at the ends, with the ends being surrounded by wrap-around holding bases, in turn secured to a mounting surface.
Each holding base is in the form of an angle-iron, of which one element has a slot running parallel to the element underside, and the upper side of the other element has a longitudinal recess. By means of these, the holding bases are stuck on opposing faces of the assembly sheet, and together with it form a holding frame for the infra-red lamp. The lamp is held between bases, and thus is received by the longitudinal recess of the holding base.
The holding frames are provided with fastening bolts. The holding bases are secured to the sheet by butterfly nuts on the backside of the assembly sheet, and are secured with a high-temperature-resistant spring. For mounting and unmounting of the individual infra-red lamps, the nuts and springs have to be released.
The electrical connections for the heating coils of the individual infra-red lamps are accomplished in the form of two insulated cables at a common end face of the twin tube, the cables are bent 90.degree. to the assembly frame, and fed through two grooves of the holding base, threaded through corresponding holes in the holding frame, and fed to the back side of the assembly frame, where they are finally connected to power supply. In order to swap out or exchange an infra-red lamp, the existing electrical connections must be removed and, when the new infra-red lamp is mounted, new connections must be wired.
On a single assembly frame, multiple parallel infra-red lamps are fastened, with lengths matched to the dimensions of the assembly frame. By modular addition of multiple assembly frames to form a larger unit, one can build surface irradiators whose irradiating surface corresponds to that of the goods to be irradiated. If necessary, the assembly frames can also be arranged perpendicular to each other, so that the longitudinal axes of the infra-red lamps are rotated 90.degree. to each other.
The assembly frames are available in two different standard lengths, matched to the infra-red lamps. The length of the larger assembly frame corresponds to twice the standard breadth, and to twice the standard length, of the smaller assembly frame. With these standard radiating units, it is possible, in the sense of a modular system, to alter the geometry of surface radiators and to adapt them to the goods to be heated, but the least little geometric variation is determined by the dimensions of the smaller assembly frame. For a change in the geometry of a surface irradiator, made of known lamp units, the assembly frame and the infra-red lamps bus be separated, and re-mounted in the desired configuration.
The wall thickness of the holding base, in the direction of the longitudinal axis of the infra-red lamp, is relatively large, first, because a certain insulation is prescribed to prevent flash-over or arcing between adjacent power supply parts, and second, because the bending of the electrical connectors within the holding base cannot go below a minimal radius of curvature, since otherwise the connecting wires would snap off. Thus, the known radiating units form relatively long unheated zones at the end faces of the infra-red lamps, and upon assembly of these irradiating units, the inhomogenous temperature course at these places becomes apparent.